1. Field
The present disclosure relates to an apparatus and method of charging a mobile terminal using an energy harvesting device.
The present disclosure is derived from (i) research conducted by a university ICT research center fostering work by the Ministry of Science ICT and Future Planning: [Project No.: 1711026714(R0992-15-1021), Project title: Development of Technology of Energy Harvesting for Wearable Device and Wireless Power Transmission] and (ii) research conducted by National Research Foundation(NRF) of KOREA grant founded by the Ministry of Education and Science Technology (MEST) through Mid-career Research Program: [Project No.: 2016R1A2B3009423].
2. Description of Related Art
Energy harvesting technology, harvesting energy discarded nearby and converting it into electrical energy to use, is expected to be prominent as a future industrial technology field promoting the preservation of the natural environment.
When used in existing electronic devices, or the like, such technology may allow electronic devices to be independently driven using nearby energy without the necessity of charging a battery using a separate power source, as well as significantly enhancing energy efficiency. Also, this technology has potentially wide application coverage for use as a power source or an auxiliary power source for various sensors and communication devices using the same.
The energy harvesting technology may be classified as harvesting solar energy from sunlight, harvesting thermoelectric energy to produce electrical energy using the Seebeck effect, based on a temperature difference, and harvesting piezoelectric energy to obtain electrical energy from sources of kinetic energy such as ambient vibrations or impacts.
Here, piezoelectric energy harvesting technology in which energy is obtained from a movement (or a motion) of a human body using a piezoelectric material attached to a user's skin or a user's clothes or footwear, such as shoes, converts vibrations or impacts, far smaller than those found in existing waterpower generation, thermal power generation, wind power generation, and tidal power generation using magnets, into electric energy, even in dark areas or a night without the presence of sunlight, and has high energy conversion efficiency.
Piezoelectric energy harvesting technology is commonly encountered in the igniters of gas lighters and gas stoves that people frequently use, and is anticipated to be extensively applied to applications in devices such as power storage devices of mobile devices, power generators of streetlights or emergency stairways, micropiezoelectric generators of micro-miniature devices, artificial internal organs as well as health examination devices, office remote control systems, structure diagnosing systems using wireless sensors, and the like.
Similar to the piezoelectric energy harvesting technology is an electrostatic energy harvesting technology obtaining energy by repetitively inducing triboelectrification in objects. According to this technology, electricity is generated on a contact surface through friction and the electricity generated thereby is stored and utilized in generators, having advantages in allowing harvesting devices obtaining a high energy output to be manufactured at relatively low cost, without an environmental contamination element.
Such harvesting technology may be applied to energy harvesting based on activities of the human body, and to this end, the piezoelectric energy harvesting technology and the electrostatic energy harvesting technology, among various harvesting technologies, may be used. A great amount of energy may be obtained from the motions of walking or running from among various human body activities, and piezoelectric devices formed of materials such as dielectric elastic composites, dielectric elastomers, polyvinylidene fluoride (PVDF), and the like, may be placed on the bottom of shoes to convert pressure applied to the devices due to the motions of walking or running into energy to thus harvest the energy. When a device with a high degree of electrification (or chargeability) is positioned in shoes and repetitive friction based on human body activities is induced, electricity may be generated on a contact surface of the device with high electrification through interfacial friction of a material, thereby allowing energy to be harvested.    Related art is Korean Patent Laid-Open Publication No. 2013-0092758 (Entitled: “Self-power Generation Device of Shoe Sole, publication date: Aug. 21, 2013).